Countrywoman Gavrilova had a bigger test against qualifier Andrea Petkovic, taking two hours and 11 minutes to record a 7-6(3) 6-4 victory. Gavrilova now faces the No.4 seed Elina Svitolin

It was a more difficult day for Australian men in Miami. John Millman surrendered an early lead against Kei Nishikori, who went on to claim a 7-6(4) 4-6 6-3 victory and Matt Ebden lost in straight sets to Australian Open semifinalist Hyeon Chung.